By John Evans Special to Yahoo Sports

Let’s say you’re choosing between two muscle cars for a Fast and Furious-style street race. Both options have oodles of horsepower, electrifying acceleration and blinding top-end speed. However, one car is equipped with Michelin’s finest high-performance tires and the other must make do with four cheap, off-brand tires of different makes. It’s a factor that won’t decide every race, but over say, 16 of them, it will influence the outcome several times.

That’s the kind of tiebreaker that offensive lines can be when you’re deciding between running backs in fantasy. Early-round picks are especially critical in your draft, and ball-carriers bust more often than receivers. Most players you’ll consider in the first two rounds are extremely talented and have comparable workloads, so the quality of their run-blocking makes an excellent decider when you’re torn between two players.

The four guys here are all studs who should produce plenty of fantasy points, but the performance of their offensive lines will impact their scoring potential. With any running back there are many other important pros and cons to take into account, but for our purposes I’ll focus mostly on the big guys who pave the way for them.

Kareem Hunt, Kansas City Chiefs

A third-round pick in 2017, Kareem Hunt wasn’t an athletic marvel coming out of Toledo. He profiles as a back who is more reliant on his offensive line than some. Hunt is a reliable, no-nonsense runner, but he’s not a creator with the ball in his hands who needs only a sliver of daylight to explode for big gainers. Assuming the Chiefs’ depth isn’t tested by injury this year, their blocking should be fine most weeks. That said, a lot can go wrong here.

Though the line’s right side is formidable, the Chiefs were below average last year on left end runs. Swiss Army knife Cameron Erving seems poised to shed his bust label at left guard, but he’s already battling a knee injury. There is at least some correlation between the alarming dip in Hunt’s production last year and the health of his blockers. K.C. suffered no calamitous injury – the line’s mainstay, right tackle Mitchell Schwartz, played all 16 games – but the shuffling of banged-up players in and out of the lineup seemed to slow Hunt’s torrid pace to start the year.

Though the starters’ missed games don’t perfectly parallel Hunt’s struggles between Weeks 8 and 13, the domino effect of injuries to center Mitch Morse and Laurent Duvernay-Tardif forced Zach Fulton to play multiple positions with varying degrees of success. (Now in Houston, Fulton won’t be there to fill in this year.) Bottom line – the team didn’t suffer unusually bad injury luck, and they still struggled to cope with it.

In a high-powered offense, it’s possible that Hunt justifies his lofty ADP with a campaign as good or better than 2017’s RB4 finish, especially if touchdown luck is on his side. But for a variety of reasons I don’t think he leads the league in rushing this year. If I’m on the clock with the ninth pick, I’d rather take…

Last year the Jaguars provided their running backs the league’s second-best yards-before-contact average and accumulated more rushing yards than anyone. The right side of the line ranked in Football Outsiders’ top 10 for adjusted line yards. Even when Fournette missed time, Jacksonville backs were effective. Now the team added coveted free agent Andrew Norwell, an All-Pro for Carolina last year who immediately solidifies the interior of this line. Paired with powerful pivotman Brandon Linder, Norwell will help the Jags improve their biggest weakness last year, which was the mid/guard run. Norwell is also an agile pulling guard – get him in space and he can spring a back for the long runs Fournette has the speed to finish.

Under old-school football czar Tom Coughlin, the Jaguars’ philosophy revolves around controlling the line of scrimmage on both sides of the ball. They’re trying to build a champion that looks more like the 2014 Seahawks than the 2016 Patriots. Jacksonville lacks the X factor that Russell Wilson brings to the equation, but the team plays to its strengths by focusing on defense and running the ball. At the same time, the Jaguars have a threatening group of speedy young receivers who will keep defenses honest.

With his rare blend of burst and power, Fournette can take full advantage of the opportunities his bruising o-line gives him. If their lines were equal, I would give Hunt the edge, based on Fournette’s injury history and the fact that Hunt was simply the superior player last year. But this is a case where the blocking each player can expect to receive tilts the scale toward Fournette.

Christian McCaffrey, Carolina Panthers

The Panthers are making public declarations about increased carries for Christian McCaffrey, but it may not matter – their offensive line is in tatters. The aforementioned Andrew Norwell was a big loss and their next best lineman, Daryl Williams, suffered a serious knee injury in practice that will reportedly sideline him until at least midseason or possibly even next year. Sophomore Taylor Moton was already slated to step into Norwell’s spot, but now he must take on the even greater challenge of playing right tackle. The former Michigan Wolverine played both positions in college, but he was mostly a special-teamer in his rookie campaign. The competition is on to see who starts at left guard… Odds are that whoever wins, he won’t be a devastating run blocker.

Which brings us to the second-year man from Stanford. A lot of McCaffrey’s fantasy value comes as a pass-catcher, obviously, as he was RB9 in PPR and RB16 in non-PPR last season. (The default setting in a Yahoo league is half-PPR). The rookie struggled running the ball between the tackles, however. By Football Outsiders’ metrics Carolina’s run blocking was well below average last year, so that may have had something to do with it, but the 2017 unit had Norwell and Williams. McCaffrey will be met at the line much more often this year and forced to grind out tough yards to secure even modest gains. He has yet to show that ability at the pro level.

CMC also has more competition for targets this year, so fantasy gamers taking him at his ADP are counting on improvement in the running game. Depending on scoring format, McCaffrey is going between pick 17-20 in most leagues, making him RB11 or RB12. At that price you’re buying him at his 2018 ceiling, unless it’s PPR. I’m a McCaffrey fan, but I predict his numbers go down, not up. Right now this next fellow is RB14 (LeSean McCoy is RB13) in non-PPR, which is tremendous value.

Fresh off developing blue-chippers Mike McGlinchey and Quinton Nelson at Notre Dame, offensive line coach Harry Hiestand returns to the Chicago staff. In his previous stint with the Bears Hiestand helped Olin Kreutz and Jamon Brown become Pro Bowlers. His new charges include three outstanding run blockers, at least when oft-injured Kyle Long is in the lineup. A lot depends on the readiness of rookie James Daniels, who excelled in the run game at Iowa, but by October the Bears backs should be the beneficiaries of fine blocking.

And by backs, I mean Jordan Howard, mostly. Tarik Cohen is a satellite back whom new coach Matt Nagy should use creatively, but in no way is this a traditional committee backfield – Howard has the early-down role on lockdown and virtually no competition for goal-line work. A powerful runner, Howard broke the 1,000-yard mark in each of his first two seasons on mostly moribund offenses with few red-zone opportunities. When he’s been there, he’s converted, but last year Chicago was a slow-paced offense that finished 30th in total yards. Only the Luckless Colts scored fewer offensive touchdowns. Somehow Chicago was last in the NFL in pass attempts in 2017 AND just 18th in rushing attempts. (Basically, John Fox tried to run out the clock on every game.)

Nagy doesn’t need to set a Chip Kelly pace for Howard to get plenty of carries. With an array of new weapons and a modern offense, the Bears will be more efficient in 2018. Give me Howard over McCaffrey – even in a PPR league.